What is Pickaxe Mountain, Iran’s underground nuclear facility Trump is threatening to attack?

With the conflict between the US and Iran facing its most sustained outbreak of violence since a ceasefire was agreed in April, Donald Trump has returned to threatening Iranian nuclear sites.

The current run of US strikes is aimed at forcing Iran to reopen the strait of Hormuz, but in comments on Tuesday, the president said that his administration remained committed to stopping Iran obtaining a nuclear weapon, and reiterated threats against a site linked to the country’s nuclear programme.

Referring to Pickaxe Mountain – known in Iran as Kuh-e Kolang Gaz La, a fortified underground site near one of the country’s primary nuclear enrichment facilities – Trump told reporters that the military would be “hitting that area pretty soon, and very heavily”.

Here’s what we know about Pickaxe Mountain.

Where is Pickaxe Mountain?

Pickaxe Mountain is ⁠located 220km (140 miles) south of ⁠Tehran and 2km (1.2 miles) from the ​Natanz nuclear facility. The Natanz site, where two of Iran’s uranium enrichment plants are located, has been bombed before; during the war started by the US and Israel on 28 February, and during the 12-day war of 2025.

Little is known about the complex located inside the mountain, but experts believe it is still under construction and estimate it is buried almost 100 metres inside the mountain.

The facility at Pickaxe Mountain was not targeted in either of the rounds of US-Israeli strikes in 2025 and 2026, according to the Institute for Science and International Security (ISIS), a US-based thinktank focused on nuclear non-proliferation.

What is the history of Pickaxe Mountain?

Construction of the facility at ‌Pickaxe Mountain began in 2020, according to the ISIS thinktank, after ‌what Iranian authorities reported at the time as an explosion caused by an act of sabotage at the Natanz facility.

Iran said at the time the Natanz sabotage had caused significant damage, and in September of that year, Iran’s then nuclear chief, Ali Akbar Salehi, said the country had started building a “modern, larger and more comprehensive hall in all dimensions in the heart of the mountain near Natanz” for making advanced centrifuges. These machines spin uranium at high speeds to enrich it and produce nuclear fuel.

Rafael Grossi, the chief of the International Atomic Energy Agency (IAEA), said in March that Iran had previously announced its intention to have nuclear activity at Pickaxe Mountain.

“This was part of their quite systematic intention to put their most sensitive facilities underground,” he said.

What has Iran built at Pickaxe Mountain?

The ISIS thinktank, which has analysed satellite imagery of the site, says it features two pairs of entrances and that a security wall around the facility was recently completed.

Since the US and Israel began launching strikes, a pair of eastern tunnel portal entrances has been hardened and partially backfilled to obstruct ground vehicle access, but they have not been ​sealed fully, the thinktank reports.

Sam Lair, a fellow at the Foreign Policy Research Institute, who also reviewed recent satellite imagery of the site, told Reuters that increasing the strength of the tunnel entrances would complicate “targeting with penetrating munitions like bunker busters”.

Is Pickaxe Mountain functioning and what could it be used for?

Trump’s threats to target the mountain earlier this month also included an admission from the president that US intelligence sees “no activity there”.

“They’re not doing well with their nuclear situation. Every time we hear about it, we blow it up. So they don’t like talking about it. But we’ll probably give Pickaxe a shot relatively soon,” he said.

The ISIS thintank, ⁠in its report, said its assessment “is that the facility is not yet operational, but construction continues”, and that it was unclear when ​it could be operational, based on satellite imagery alone.

The thinktank says it is also unclear ​if Iran still plans on installing a large-scale assembly facility there.

“Nonetheless, if Iran starts to rebuild its centrifuge manufacturing ​capability, it could plan to install ‌a smaller centrifuge assembly facility in ​Pickaxe Mountain able to serve a nuclear weapons ​program,” the ISIS report said.

How might Pickaxe Mountain be attacked?

Experts assess the deeply buried complex as being beyond the reach of the most powerful bunker buster bombs in the US arsenal. Aerial attacks also carry a degree of uncertainty, because assessing their effectiveness can be difficult without on-the-ground intelligence. A Pentagon report issued after the US launched strikes on Iran’s nuclear sites in 2025 said the damage caused likely set back the nuclear program by one to two years, but that conclusion came with a large amount of uncertainty.

The ISIS thinktank said the site “would be more suitable for ground forces to attack or sabotage … however, vulnerabilities may also exist that can be exploited by deep earth penetrating weapons via aerial attacks.”

The deployment of ground operations have so far been a red line for Trump and there has been no suggestion that he is any closer to considering such a move, even after the recent escalation between the US and Iran.

Lair said: “We can infer that there are ongoing activities at Pickaxe Mountain the Iranians wish to continue, but are still concerned enough about a potential attack that they are taking steps to bolster their defences.”

With Reuters